Two distinct phases characterize maturation of neurons in the nucleus of the tractus solitarius during early development: Morphological and electrophysiological evidence

We have used electrophysiology and light microscopy of intracellularly labeled neurons in the nucleus of the tractus solitarius (nTS) in brainstem slices of the newborn rat (PO to P6) to examine the functional and morphological correlation of their development. Three-dimensional reconstruction of neurons injected intracellularly with biocytin, following electrophysiological recording, revealed a close correspondence between morphological immaturity (appearing as polarization of the dendritic tree) and the absence of a ramp-like voltage trajectory at the offset of hyperpolarizing current injections–l_A negativity (8 of the 8 cells examined showed this correlation). These morphologically polarized I_A negative neurons showed preferential dendritic sprouting in two diametrically opposite poles of the perikaryon. The orientation of the polarity differed according to the rostrocaudal location of the neuron. The appearance of a polarized dendritic tree during the first (immature) phase was transient and closely coincident with I_A negativity. Following the development of adult-like electrophysiological characteristics, i.e., I_A positivity, nucleus of the tractus solitarius neurons showed remarkably different morphological features (9 of 10 cells). These included a widespread branching of the dendritic tree in all directions, giving it a bushy appearance (cell body to dendrite ratio of 1:40). Numerous dendritic spines, growth cones on both dendrites and axons, and axon collateralization were present during both phases and indicate that nTS neurons during the two phases of early development demonstrate dynamic features of growth and maturation. The development of adult-like electrophysiological characteristics, i.e., I_A positivity, progressively increased in the postnatal period. During the later part of the first postnatal week, twice as many neurons showed I_A positivity in days P3 to P6 as compared with days PO to P2. These results reveal the dynamic nature of neurons in the nTS during early development and illustrate the close link between morphology and functional characteristics in this region. We suggest that the establishment of adult-like morphology can be modified by appropriate environmental clues provided to nTS neurons during the initial (immature) phase of early postnatal development. © 1993 Wiley-Liss, inc.     

Injury and strain-dependent dopaminergic neuronal degeneration in the substantia nigra of mice after axotomy or MPTP

We studied the effects of axotomy or neurotoxin on the survival of substantia nigra pars compacta (SNpc) neurons in two strains of mice, FVB/N or C57BL/6. Fluoro gold (FG) was injected into both striata of the mice to retrogradely label the nigrostriatal neuronal population. Ten days later, these neurons were axotomized in the medial forebrain bundle (MFB) unilaterally or N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was administered intraperitonealy for 2 days to produce bilateral degeneration. MFB transection or MPTP administration produced a progressive loss of FG-labeled and tyrosine hydroxylase immunolabeled (TH+) neurons in both strains. Relative to control, 72% of SNpc neurons died 4 weeks after axotomy in C57BL/6 mice and 50% died after axotomy in FVB/N mice. MPTP resulted in death of 80% of SNpc neurons in C57BL/6 mice but only 40% in the FVB strain 4 weeks after MPTP administration. In this more sensitive strain, MPTP cell death was associated with positive staining for terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and nuclear condensation. In contrast, no TUNEL staining was detected in SNpc after MPTP in FVB/N mice. Further, while similar kinetics and extent of cell death accompanied axotomy, axotomy-induced cell death was TUNEL negative in both FVB/N and C57BL/6 mice. Double staining for TUNEL and microtubule associated protein 2 confirmed that the majority of the TUNEL positive cells were neurons. These data indicate that genetic factors and the type of lesion play an important role in determining death of dopaminergic neurons after injury.     

Increased glomerular and urinary malondialdehyde in puromycin aminonucleoside-induced proteinuria in rats

Puromycin aminonucleoside (PAN)-induced proteinuria in rats may be mediated by reactive oxygen metabolites (ROM), which are injurious to several cell components including membrane lipids. Increased malondialdehyde (MDA) production is indicative of lipid peroxidation. We examined if MDA content of glomeruli and its urinary excretion were increased in rats administered PAN. Of three groups of 8 Sprague-Dawley rats each, group 1 served a control, group 2 animals received a single intravenous injection of PAN (5 mg/100 g body weight) and group 3 animals PAN with intraperitoneal injections of dimethylthiourea (DMTU), a free radical scavenger of oxidants such as hydroxyl radicals, for 4 days. The rats were sacrificed on day 8 after PAN injection. Increasing proteinuria, starting on day 4, developed in animals in group 2 but not in the others. The glomerular MDA (nmol/mg protein) in group 2 animals was 2.93±1.91, significantly higher than 0.87±0.63 and 1.26±0.76 in groups 1 and 3, respectively. urinary levels of MDA markedly increased in group 2 rats on day 3 and remained high thereafter, but no such increase occurred in the control animals and those administered PAN with DMTU; the latter was thus protective against PAN toxicity. Our observations support the view that ROM are involved in PAN-induced glomerular injury and that increased urinary MDA excretion can be a marker of ROM-mediated lipid peroxidation.     

Rapidly adapting pulmonary receptor afferents: I. Arborization in the nucleus of the tractus solitarius

The organization of axon collaterals, preterminal processes, and presumptive synaptic boutons of single physiologically identified rapidly adapting receptor (RAR) pulmonary afferent fibers was examined following the intraaxonal application of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP). The RAR axons were injected 200-300 microns lateral to the nucleus of the tractus solitarius (nTS) at a number of different rostrocaudal levels in seven individual experiments. The trajectories of the stained axons were reconstructed from individual 50-microns-thick serial sections. The rostrocaudal extent, as well as the distribution of the trajectory of each RAR afferent, was reconstructed from every section by using a camera lucida attachment. In this first of two papers, we describe the pattern of organization of bouton terminals of RAR afferents related to cytoarchitectonically distinct subnuclei of the nTS. In the companion paper, morphological details of the fine structure of these synaptic boutons and axonal branches are described in different subnuclei in order to illustrate morphological differences in these functionally distinct regions. A number of significant findings have resulted from this light microscopic study. The central process of a single RAR afferent fiber arborized in the medulla oblongata over a considerable distance in the rostrocaudal plane (2.5 mm rostral to 1.4 mm caudal to the obex). A single RAR afferent fiber terminated in numerous bouton terminals (range 500-1,050), and these terminals arose from over 400 segments of branches of the parent injected axon. A small number of en passant bouton terminals were found. There appeared to be a remarkable degree of consistency in the subnuclei of the nTS where these terminals arborized. The dorsal and dorsolateral subnuclei of the nTS received 144-647 bouton terminals. The second-largest concentration of bouton terminals of RAR afferents was found in the intermediate (nI) subnucleus of the nTS. No labeled bouton terminal was found in the ventral and ventrolateral subnuclei of the nTS. This finding is in sharp contrast to the terminations of SAR afferents which terminated predominantly in the ventral and ventrolateral nuclei of the nTS, the interstitial nucleus of the nTS, and the nI. The parent RAR axon could be traced as far rostrally as 2.5 mm, even though the region of terminal arborization could not be followed beyond 0.8 mm. The destination of this rostrally projecting RAR afferent could not be determined in this study.(ABSTRACT TRUNCATED AT 400 WORDS)     

鸦胆子化学成分的研究

继从中药鸦胆子Brucea javanica (L.)Merr的果实中分得一系列具抗肿瘤活性的苦木内酯成分后,又进一步分得一新生物碱和一新苦木内酯,通过理化常数和光谱(UR,IR,~1HNMR,~(13)C NMR)分析,推断其结构分别为4-乙氧甲酰基喹诺-2-酮(4-ethoxyca-     

Emerging strategies for the transdermal delivery of peptide and protein drugs

Transdermal delivery has been at the forefront of research addressing the development of non-invasive methods for the systemic administration of peptide and protein therapeutics generated by the biotechnology revolution. Numerous approaches have been suggested for overcoming the skin's formidable barrier function; whereas certain strategies simply act on the drug formulation or transiently increase the skin permeability, others are designed to bypass or even remove the outermost skin layer. This article reviews the technologies currently under investigation, ranging from those in their early-stage of development, such as laser-assisted delivery to others, where feasibility has already been demonstrated, such as microneedle systems, and finally more mature techniques that have already led to commercialisation (e.g., velocity-based technologies). The principles, mechanisms involved, potential applications, limitations and safety considerations are discussed for each approach, and the most advanced devices in each field are described.